The present invention generally relates to guidance control systems for implements that trail a motor vehicle.
In the farming industry, guidance systems for controlling the position of trailing implements, particularly those which are mounted to the three point hitch of a motor vehicle, have been developed and marketed for many years. The design of some of the types of systems has limited their effectiveness and accuracy with regard to positioning the implement. Guidance systems that have exhibited reliable and accurate operation are those manufactured and marketed by Sunco of North Platte and Madrid, Nebr.
The Sunco systems are marketed under the trademark AcuraTrak® have exhibited superior operating characteristics for guiding many types of trailing implements that are pulled by farm tractors. While some guidance systems are designed to be more concerned with controlling the tractor itself, the AcuraTrak system is designed to control the lateral position of an implement relative to the tractor that is pulling it, with the focus being on proper positioning of the implement along a desired path as the implement is pulled through a field during operation. The currently marketed Acura Track guidance systems operate in a manner based on principles that are set forth in U.S. Pat. Nos. 5,240,079, 5,150,849 and Re. 34,080, and are generally applicable to certain aspects of the present invention. All of these patents are specifically incorporated by reference herein.
The guidance systems disclosed in those patents utilize a wand mechanism associated with the implement which is dragged along the ground and is a common means for sensing the relative position of the implement relative to the rows. The wand is mounted on the implement in a manner that it is positioned in the middle of the distance between two adjacent rows. The midpoint between two rows is usually the lowest point between the rows, since a cultivating operation tends to move dirt from the middle toward the plants, for example. The wand is angularly moveable so that its angular position can change depending upon whether the implement is oriented in the center between adjacent rows or is offset from the center. Thus, if the implement is moving to one side of center to the other, the angular position of the wand will change and provide corrective signals for controlling the guidance system to alter the lateral position of the implement relative to the rows.
It should be easily understood that if an operator is cultivating a crop that has already reached a stand, or is planting or marking out rows, or the like, the difficulty does not reside in the operator being able to keep the tractor between the rows without the tractor wheels crushing the crop, but rather keeping the implement from getting too close to the crop which could, in the case of cultivation, result in damage to the roots of the crop by the cultivator blades. In the case of marking out rows, it is obviously desirable to have uniform rows.
With the advent of global positioning systems (GPS), it has been the desire, if not the goal of many in the agricultural industry to use GPS systems as the navigation tool to control tractors during a planting or other farming operation to make and/or follow rows that are properly aligned in a field and relative to other rows. Improvements in the GPS signals now enables positioning within a tolerance of an inch or less during a farming operation, and also enables accurate mapping of paths that a vehicle should travel.
While such guidance systems as described above are effective, particularly when coupled with GPS systems and are connected to a three-point hitch of a tractor or other type of motor vehicle, there are still significant challenges to existing guidance systems that operate in connection with an implement with an elongated tongue having a forward end that is pivotally connected to a drawbar, and the rear end fixedly connected to the body of the implement and preferably to the tool bar. Such an implement will be referred to herein as a “tongued implement”.
Providing guidance of such tongued implements has been attempted by forcing the drawbar laterally relative to the tractor, but such forced lateral movement simply does not work well, particularly on sloped land where gravity creates side forces that dramatically affect the operation of the tractor and drawn implement combination.
While other prior solutions included U.S. Pat. No. 5,025,866 which had a tongue driven by a hydraulic cylinder at the rear end of the tongue where it is pivotably connected to the tool bar and the angle is changed by operation of a hydraulic cylinder, that solution is impractical for extremely large implements that may cover 20 to 30 rows of crops in a single swath, because of the extremely large forces that would generated by implements of such size on a pivotable connection between the tongue and the tool bar.
The difficulty that is experienced in the operation of tongued implements being drawn by a tractor is described in connection with FIGS. 1 and 2 where a tractor, indicated generally at 20, is pulling an implement, indicated generally at 22, along a path 24 that has a down slope to the right as indicated by the arrow, such as would be the case on a side hill. The down slope is defined to be where the tractor 20 is located in FIG. 1 and extends only to the position slightly ahead of the tool bar 32, with the implement 22 being on level ground.
The tractor has rear wheels 26, front wheels 27 and a drawbar 28 that is connected to the tractor at 30 and is kept from pivoting around connection 30 by conventional hitch structure so that it is oriented along the center line of the tractor as indicated. The implement 22 has a tool bar 32 to which eight planter row units or other implements 34 are attached, with the implement riding on a frame structure (not shown) to which wheels 36 are mounted. The implement 22 has a tongue 38 rigidly attached to the tool bar 32 and is preferably supported by braces 40 to insure that the 90° angle between the tongue and the tool bar is maintained during operation. The front end of the tongue is pivotally connected to the drawbar 28 at 42 which defines the pull point for the implement.
As shown in FIG. 1, because of the slope that was encountered during forward movement, the tractor rear wheels 26 have started sliding to the right or down the hill, which moves the pull point to the right pulling the implement 22 downhill before the implement gets to the slope. As the tractor rear wheel 26 slides to the right, the pull point 42 is pushed to the right and as shown in FIG. 2, the implement remains off track, i.e., the wheels 36 do not follow the track 24 as long as the rear wheels 26 of the tractor 20 are off track.
As previously indicated, prior ineffective guidance attempts included forcing the drawbar laterally from side to side. This is shown in FIG. 3 where the drawbar 28 has been pivoted around the connection 30 to one side by 15 inches. Thus, the pull point defined by the connection 42 is 15 inches to the right of the center of the tractor which has the tendency to pull the rear of the tractor off the path and significantly increases the side load on the tractor which results in substantial inefficiency.
Such movement of the drawbar from side to side in the manner shown in FIG. 3 is known to be ineffective in steering the implement and such drawbar steering simply does not work as is evidenced by the fact that there are few commercial products in the marketplace that attempt to utilize such operation for providing guidance. It is important that the pull point be maintained generally in the center of the tractor to have effective and efficient operation.